This invention relates to improvements in viscous torsional vibration dampers and is more particularly concerned with improving the reliability and lowering the cost of such dampers.
Viscous torsional vibration dampers of the kind to which the present invention is directed have heretofore been successfully produced with cast ferrous, forged ferrous, stamped, and welded housings all machined to provide the desired dimensions, providing an axially opening annular working chamber within which is housed a complementary annular inertia mass ring and with a cover sealed across the axial opening of the housing for confining the inertia ring within the annular working chamber therein. Opposed surfaces of the inertia ring and the housing are in shear film spaced relation having regard to a viscous damping fluid substantially filling those spaces. Cast, forged, and stamped and welded housings require much machining, and therefore present a substantial cost factor in the dampers.
A further proposal has been to finish shape the damper housings by hydroforming techniques. This necessitates rather wide tolerances and therefore unusually high viscosity damping fluid, unless the shear film gap surfaces are machined, consequently resulting in a costly construction. By way of example Pat. No. 3,512,612 is referred to for a disclosure of the hydroforming proposal for such dampers.